CN111426552A - A method for analyzing the mechanical properties of 3D printed specimens with different build orientations - Google Patents

Abstract

The invention discloses a method for analyzing the mechanical properties of 3D printing samples with different construction orientations. The spline is placed in the loading device, and the loading device is debugged; the mechanical property testing test is carried out, and the image of the sample spline during the test is collected; the digital image correlation method is used to compare and analyze the image of the sample spline before and after deformation, and obtain the pixel Point displacement and strain information; according to the strain information, the stress-strain curve is obtained, and the performance parameters of the sample spline are obtained; the above steps are repeated to complete the mechanical property testing test of a variety of sample splines with different construction orientations, and the mechanical properties of the sample splines with different construction orientations are analyzed. Differences in mechanical properties of specimen splines.

Description

A method for the analysis of mechanical properties of 3D printed specimens with different build orientations

technical field

The invention belongs to the technical field of mechanical property detection in the additive manufacturing industry, and particularly relates to a method for analyzing the mechanical properties of 3D printing samples with different construction orientations.

Background technique

The statements herein merely provide background related to the present invention and do not necessarily constitute prior art.

Mechanical properties measurement methods are divided into electrical measurement methods and optical measurement methods in principle. Electrical measurement methods include resistance strain gauges, capacitance strain gauges, etc. The electrical measurement method is widely used in the laboratory due to its simple operation. It belongs to contact measurement, which is restricted by test conditions in many complex situations (such as high temperature, low temperature or magnetic field), and often cannot meet the test requirements. On the other hand, engineering tests often require a large number of strain gauges to be pasted on the surface of the sample, which also brings cost problems due to the non-reusability of strain gauges.

Digital image correlation (DIC) is an optical method based on the principle of correlation before and after the deformation of the measured object. The deformation analysis method has the advantages of full-field, non-contact, real-time and low environmental requirements.

When analyzing the mechanical properties of materials, it is usually assumed that the material is continuous and uniform, without considering the defects or cracks of the material itself, but the anisotropy of products in the manufacturing industry can be seen everywhere, especially in the additive manufacturing industry, due to its unique layer-by-layer The manufacturing process of build-up molding makes the samples show obvious anisotropy. In the additive manufacturing industry, the stiffness, strength, and stability of the sample will be affected by different factors such as the set filling density, printing speed, base plate temperature, needle temperature, and layer thickness. Changes in any one condition will affect the mechanical properties of the product, as well as the surface finish and so on. 3D printing rapid prototyping technology is an emerging additive manufacturing technology that is rapidly developing in the manufacturing field. It is known as "a manufacturing technology with industrial revolution significance. The research on how to improve the performance of printed products has also been concerned in recent years. It has benefited from the integration of cutting-edge technologies in multiple disciplines, which has given it a certain reputation in the fields of aerospace, national defense, biomedicine, government, medical equipment, high-tech, education, manufacturing, automobiles and motorcycles, and home appliances. Application and development prospects are very broad. So far, there are more and more types of printing technologies, but when it comes to printing technology, Fused Deposition Modeling (FDM) technology cannot be avoided. It is a complex process with a large number of The parameters that affect product quality and material properties, the combination of these parameters is often difficult to understand. Bi Yongbao et al. used wheat straw powder and PLA to prepare biomass composite printing materials by exploring different filling densities, layer thicknesses, printing speed and temperature conditions. The mechanical properties of the composite product were studied, combined with the experiment to obtain the best printing method under the corresponding conditions. Raunt et al. considered the influence of the placement angle on the mechanical properties of the product. Shu You et al. Starting from these factors, we explored the effect of different conditions on the mechanical properties of 3D printed degraded L-polylactic acid (PLLA) samples. There are also many parameters such as build direction, layer thickness, grating angle, grating width, and air gap, etc., which have an impact on FDM printed parts It has a great impact on the quality and performance of the 3D printing technology. Since 3D printing technology has been quite mature, in recent years, more and more domestic and foreign researchers have paid more attention to the setting of printing parameters, or the blending of modified substances with printing materials. Many scholars have studied the mechanical properties of samples from the settings of various printing parameters, but few scholars have studied the mechanical properties of their products from measurement methods.

Since mechanical properties are very important to functional parts, and the mechanical properties of samples formed with different constructions are quite different, and domestic and foreign experts and scholars have little research on the mechanical properties of printed samples formed with different construction orientations, it is absolutely necessary to check the process. Influence of parameters on mechanical properties. Therefore, it is necessary to further study the differences in the mechanical properties of components caused by different printing parameters, but the inventors found that the prior art did not consider the analysis of the differences in mechanical properties of components, especially regarding the mechanical properties of components processed by low-cost 3D printers. Analysis of differences in mechanical properties of parts is even rarer.

SUMMARY OF THE INVENTION

Aiming at the deficiencies of the prior art, the purpose of the present invention is to overcome the shortcomings of the prior art, seek a method for testing the mechanical properties of printed samples, and provide a method for analyzing the mechanical properties of 3D printing samples with different construction orientations. The digital image correlation method is applied to the additive manufacturing industry, and the mechanical properties of the printed specimens with different orientations are analyzed.

In order to achieve the above object, the present invention is realized by the following technical solutions:

In a first aspect, embodiments of the present invention provide a method for analyzing mechanical properties of 3D printing samples with different construction orientations, including the following steps:

3D printing is used to make a variety of sample splines with different construction orientations, and speckle is set on the surface of the sample splines;

Place the sample spline on the loading device and debug the loading device;

Carry out the mechanical property testing test, and collect the image of the sample spline during the test;

Using the digital image correlation method, the images before and after the deformation of the sample spline were compared and analyzed, and the pixel point displacement and strain information were obtained;

According to the strain information, the stress-strain curve is obtained, and the performance parameters of the sample spline are obtained;

The above steps are repeated to complete the mechanical property testing tests of the sample splines with different construction orientations, and the differences in the mechanical properties of the specimen splines with different construction orientations are analyzed.

As a further technical solution, the steps of setting speckle on the surface of the sample spline are:

One side of the sample strip is sprayed with white matte paint, and then decorated with black matt paint to make evenly distributed speckles.

As a further technical solution, the steps of setting speckle on the surface of the sample spline are:

The surface of one side of the sample spline is sprayed with black matte paint, and then decorated with white matt paint to make evenly distributed speckles.

As a further technical solution, the loading device includes a universal testing machine, the universal testing machine is connected with the universal testing control system, a CCD industrial camera is installed in front of the universal testing machine, and the CCD industrial camera is connected with a computer; the universal testing machine is provided with a clip Hold the loading member.

As a further technical solution, when the three-point bending test is performed, the clamping and loading member includes a slideway and a loading support, the top of the slideway has a slide groove, the two loading supports are arranged on the slide groove at intervals, and the loading support The seat can slide along the chute; the test piece is placed on two loading supports, and a concentrated force applying device is arranged above the chute.

As a further technical solution, the concentrated force applying device includes a C-shaped member with an upward opening, the top of the C-shaped member is connected to the universal testing machine, the bottom end of the C-shaped member is connected to a loading rod, and the loading rod is arranged vertically; the slideway Landscape setting.

As a further technical solution, the procedure for placing the sample splines is:

Place the sample bar in the middle of the universal testing machine, so that the sample bar maintains a vertical and horizontal balance, and the speckle side of the sample bar faces the CCD industrial camera.

As a further technical solution, the process of obtaining pixel point displacement and strain information is as follows:

The images before and after deformation of the sample spline are compared and analyzed, and then the correlation calculation is performed on the sub-areas of the image before and after deformation, and the relative displacement of the pixel at the center point of the sub-area before and after deformation is obtained, so as to obtain the pixel point displacement and strain information.

As a further technical solution, the process of obtaining the performance parameters of the sample spline is as follows:

From the pixel point displacement and strain information, combined with the relationship between the loading load and time, the real-time stress-strain curve is obtained, and the strain cloud map obtained by the digital image correlation method is used to obtain the tensile strength, elongation, deformation speed and Acceleration performance parameters.

As a further technical solution, the mechanical property testing test includes a tensile test, a compression test, and a three-point bending test. Three kinds of tests are performed on the sample splines with different construction orientations in turn, and the different constructions under each test condition are analyzed. Mechanical properties of oriented specimen splines.

The beneficial effects of the above embodiments of the present invention are as follows:

The invention can accurately obtain full-field displacement strain, and measure information such as tensile (compression/bending) strength and elongation of the test piece.

The invention applies the digital image correlation method to the additive manufacturing industry for the first time, and comprehensively analyzes the mechanical properties of the printed samples formed with different construction orientations. The same is true for the changes of other printing parameters. The differences in their mechanical properties were investigated in depth.

The invention overcomes the contact measurement of the traditional method, the method can analyze the displacement, strain and stress from the microscopic view, has a wider range, higher precision, and can better reflect the real mechanical properties; it overcomes the measurement data given by the traditional measurement method. For the problems of large error and strict requirements on test conditions, this method is simple and fast to measure, and has low requirements on test conditions.

The invention overcomes the defect of the prior art that the average value of spline damage during stretching is obtained only by analyzing the pressure-time curve in the stretching process, and cannot reflect the local damage situation well, and can analyze the load of the entire test piece in real time. The whole process.

Description of drawings

The accompanying drawings forming a part of the present invention are used to provide further understanding of the present invention, and the exemplary embodiments of the present invention and their descriptions are used to explain the present invention, and do not constitute an improper limitation of the present invention.

1 is a flow chart of the steps of a method for analyzing mechanical properties of a 3D printed sample according to one or more embodiments of the present invention;

2 is a schematic diagram of a loading device according to one or more embodiments of the present invention;

Figure 3a is a schematic diagram of a standing sample according to one or more embodiments of the present invention;

Figure 3b is a schematic diagram of a side-to-side test specimen according to one or more embodiments of the present invention;

Figure 3c is a schematic diagram of a lay-flat specimen according to one or more embodiments of the present invention;

4 is a schematic diagram of the shape and size of a sample according to one or more embodiments of the present invention;

5 is a schematic diagram of a clamped loading member employed in a three-point bending test according to one or more embodiments of the present invention;

6 is a schematic diagram of an image processing flow according to one or more embodiments of the present invention;

In the picture: 1. Universal testing machine, 2. Universal test control system, 3CCD industrial camera, 4. Computer, 5. 3D printing sample, 6. Loading support, 7. slideway, 8. Concentrated force application device.

The mutual spacing or size is exaggerated in order to show the position of each part, and the schematic diagram is for illustration only.

Detailed ways

It should be noted that the following detailed description is exemplary and intended to provide further explanation of the invention. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It should be noted that the terminology used herein is for the purpose of describing specific embodiments only, and is not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the invention clearly dictates otherwise, the singular is intended to include the plural as well, and it is also to be understood that when the terms "comprising" and/or "including" are used in this specification, Indicate the presence of features, steps, operations, devices, components and/or combinations thereof;

For the convenience of description, if the words "up", "down", "left" and "right" appear in the present invention, it only means that the directions of up, down, left and right are consistent with the drawings themselves, and do not limit the structure. It is for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be construed as a limitation of the present invention.

Terminology explanation part: if the terms "installation", "connected", "connected", "fixed" etc. appear in the present invention, it should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or as a whole; It can be a mechanical connection, an electrical connection, a direct connection, or an indirect connection through an intermediate medium, an internal connection between two elements, or an interaction relationship between the two elements. In other words, the specific meanings of the above terms in the present invention can be understood according to specific situations.

As described in the background art, there are deficiencies in the prior art. In order to solve the above technical problems, the present invention proposes a method for analyzing the mechanical properties of 3D printing samples with different construction orientations.

In a typical embodiment of the present invention, as shown in FIG. 1 , a method for analyzing the mechanical properties of 3D printing samples with different construction orientations is proposed. In this method, the 3D printing samples are loaded on the loading device, as shown in FIG. 2 . As shown, the main structure of the loading device includes a universal testing machine 1, a universal testing control system 2, a CCD industrial camera 3 and a computer 4; the 3D printing sample 5 is connected to the universal testing machine, and the universal testing machine is used for 3D printing samples. For loading, the universal test control system is connected with the universal testing machine to control the start and stop of the universal testing machine. A CCD industrial camera is placed in front of the universal testing machine to monitor the loading process of the universal testing machine for 3D printing samples. For image acquisition, a CCD industrial camera is connected to a computer to save the acquired images.

This method analyzes the differences in mechanical properties of three groups of samples formed with different construction orientations. Therefore, 3D printing is used to produce three samples with different construction orientations, such as the standing type in Figure 3a, the side vertical type in Figure 3b, Figure 3c Flat lay.

The production and molding of the sample is realized by the following process:

Due to the low cost of polylactic acid materials, the maturity of fused deposition printing technology, and the extensiveness of parameter research based on this material, many experts and scholars selected fused deposition molding polylactic acid printing samples. According to GB/T 1040-2006, the standard pull Spline polylactic acid sample, the standard sample production process of this experiment is: use the three-dimensional modeling software SolidWorks to establish a standard model, use cheap and environmentally friendly polylactic acid wire, use Tiertime up box printer to slice the model, Add support and other treatments to print three sets of standard splines with different construction orientations by the fused deposition printing method;

Here, the tensile test of samples with different constructions is used as an example to illustrate. The above-mentioned loading device is used to detect and analyze the mechanical properties of tensile specimens with different constructions and orientations. The specific test method is carried out according to the following steps:

1. 3D printing is used to make tensile specimen splines with three different construction orientations;

2. Before the test, one side of the spline is sprayed with white matte paint, and then decorated with black matte paint to make suitable speckles, and vice versa.

Speckle is used as important information for comparing before and after deformation. The speckle is uniformly and randomly distributed, and the size of the speckle particles is related to the object distance, because the quality of the speckle directly affects the accuracy and precision of the results.

In order to ensure the quality of speckle formation, when spraying matte paint to the spline, a layer of gauze should be spaced between the spline and the spray nozzle; in addition, the angle and force of the spray should be changed to a certain extent when spraying.

3. When the loading device performs the tensile test, install the wedge-shaped fixture on the universal testing machine, so that the wedge-shaped fixture clamps the tensile spline; when placing the tensile spline on the loading device, the tensile spline should be vertically As well as horizontal balance, this process is achieved by adjusting the fixture and using a spirit level to ensure that no horizontal component force appears during the tensile test.

Place the printed stretch spline in the center of the universal testing machine, and turn the speckled side of the printed stretch spline toward the CCD industrial camera, so that the spline image appears in the center of the camera's acquisition computer.

4. Debug the CCD industrial camera and the universal material testing machine, and adjust the loading speed of the universal testing machine and the acquisition speed of the camera to achieve a suitable image acquisition frequency, which will affect its accuracy. Can. In this embodiment, the loading speed of the universal testing machine is adjusted to 0.1Mpa/s, and the acquisition speed is 2 frames/s.

5. The light source is also one of the important factors affecting the correctness and accuracy of the results. Generally, ordinary white light is used. There are two points that need special attention: one is that the image cannot be exposed or darkened, and the other is that during the test process Strobe effects are not allowed.

The light source adopts ordinary white light, and the DC light source can also be added or the brightness of the light source can be adjusted according to the situation on the spot, so that the lighting effect on the spot can meet the test requirements and ensure that there is no partial exposure or partial darkness on the surface of the sample.

When adjusting the brightness of the light source, observe the pictures displayed on the computer more, or try to take a few pictures to analyze them, and use DC light to fill the light to avoid the stroboscopic phenomenon. If the natural light of the test site meets the requirements, supplementary light treatment is not required.

6. After adjusting the position as described in step 4, connect the CCD industrial camera to the universal material testing machine, start the CCD industrial camera and trigger the universal material testing machine to start, and use the CCD industrial camera to collect images of the whole process of loading the test piece.

7. Use the DIC method to compare and analyze the images before and after the deformation collected by the CCD industrial camera. The basic principle of this method is to convert the topography images of the measured object before and after the deformation into digital images through a photoelectric camera or a digital camera. The sub-areas of the image before and after the degeneration are calculated to obtain the relative displacement of the pixel at the center point of the sub-area before and after the deformation, so as to obtain mechanical information such as pixel point displacement and strain.

When the method performs the search and matching of the correlation calculation, the standardized covariance correlation function selected is:

Among them: f(x, y) and g(x+u, y+v) represent the gray value of each pixel of the image respectively; f _m and g _m are the average gray value of the sub-region of the image; u, v are The displacement of the center of the subregion, in pixels;

8. According to step 7, the real-time image displacement and strain information of the sample can be obtained on the acquisition computer. With the relationship between the load and time given by the universal testing machine, the stress-strain curve can be obtained in real time, and the strain cloud map can be obtained by the digital image correlation method. , to obtain performance parameters such as tensile strength, elongation, deformation speed and acceleration of the specimen.

Based on the principle of digital image correlation method, the image can be processed by software such as MATLAB, and then these parameters that characterize the basic mechanical properties of the sample can be obtained by partial derivation and derivation.

9. Repeat the above steps to complete multiple repeated tests of three groups of samples formed in different construction directions. During the test, the pictures can be analyzed in real time, and the stress-strain relationship can be obtained by combining the data of the universal testing machine. The differences in mechanical properties of 3D printed specimens with different construction orientations under tensile tests were analyzed.

At the end of the test, the pictures collected during the test, the load time data of the testing machine and other information can also be saved for later use.

Compared with the prior art, the present invention can accurately obtain the full-field displacement strain, and measure the tensile (compression/bending) strength and elongation of the test piece.

In the same way, by replacing the sample clamping fixture in the loading device, the corresponding compression test and three-point bending test can be carried out. The test principle is the same as that of the tensile test, and will not be repeated here.

For the three-point bending test, proceed as follows:

The universal testing machine is equipped with a clamping and loading member. When performing a three-point bending test, the clamping and loading member includes 2 loading supports 6, 1 slideway 7, and 1 concentrated force application device 8, as shown in Figure 5. The concentrated force application device is processed according to the universal testing machine and can be directly installed on the indenter of the universal testing machine. The concentrated force application device includes a C-shaped member with an upward opening. The top of the C-shaped member is connected with the universal testing machine. The C-shaped The bottom end of the component is connected to the loading rod, the loading rod is arranged vertically, and its bottom end is placed above the slideway; , and the loading support can slide along the slideway, so as to adjust the position of the loading point during the three-point bending, so as to better complete the three-point bending test. The 3D printed sample 5 was placed on two loading supports during the test, and the universal testing machine loaded the sample through the concentrated force application device installed on the indenter.

When the upper part of the concentrated force application device is loaded with one end in the laboratory, make sure that it is pressed in a symmetrical position on the sample. The opening of the C-shaped member of the concentrated force application device can accommodate the supporting device of the universal material testing machine. After the concentrated force application device is fixed, it can firmly transmit the pressure to the bottom. It can be easily installed and removed during use, and can be easily installed and removed with the sample. The contact end should be polished smooth and ensure that it is always vertical during the loading process, which requires it to have a certain stiffness and stability. Before the experiment, the surface of the three points of contact with the sample should be wiped clean and coated with a thin layer of lubricant.

The bending performance of the three-point bending specimen is tested according to the GB/T 9341-2006 standard. For the three-point bending test, first of all, it is necessary to ensure that the positions of the two loading supports below are flat, and the slideway must have sufficient rigidity. Adjust the balance and fix it before the experiment starts, leaving a distance of 3cm between the loading support and the end point. Here, it is 3cm for this experiment. However, this is not a fixed amount. Different spans correspond to different pressures, which does not affect Analysis and evaluation of mechanical properties of printed splines.

The present invention applies the DIC method to the additive manufacturing industry for the first time, and comprehensively analyzes the mechanical properties of the printed samples with different construction orientations. The same is true for the changes of other printing parameters. The differences in performance are explored in depth.

The invention overcomes the contact measurement of the traditional method, and the method can analyze the displacement, strain and stress from the microscopic view, has a wider range and higher precision, and can better reflect the mechanical properties of the real printed sample.

The present invention realizes real-time analysis of pictures, and obtains basic displacement, strain, maximum flexural strength and the like in synchronization with the test to characterize basic mechanical properties such as tension, bending and compression.

At present, few scholars have conducted differential analysis on the mechanical properties of different construction orientation molding and printing samples, but the present invention can achieve this, and the basic mechanical properties such as tension, compression and bending can be easily detected and analyzed by using this method. And the results are traceable.

In the field of additive manufacturing, people are very concerned about the influence of various parameters on the mechanical properties of the sample. The present invention proposes the detection of different construction orientations, which can be extended to change the performance of other parameters. Can also be used.

The invention overcomes the problems of large error in measurement data and strict requirements for test conditions given by traditional measurement methods. The method is ingenious in design, simple in operation, low in experimental conditions, relatively high in environmental adaptability, and accurate in measurement results; the application of DIC method in the field of additive manufacturing has the advantages of digital accuracy, traceability, real-time analysis, comprehensive The advantages of field and non-contact make this method have a wide application market in this industry.

The invention analyzes the difference in mechanical properties of printing samples with different construction orientations, and performs non-contact and full-field deformation analysis on the whole process of tensile, compression, and three-point bending tests on the printed samples with different construction orientations, so as to achieve The difference in mechanical properties of the printed samples with different construction orientations is detected, which provides a reliable basis for further theoretical research, and provides a new idea for the subsequent researchers of 3D printing in the analysis of physical shape and temperature conditions.

The invention records the entire test process by means of the DIC method, and its unique full-field analysis and real-time recording function provide comprehensive and traceable convenience for later research on the mechanical properties of the sample, and provide an effective and efficient method for in-depth research on the mechanical properties of the sample. and convenient means.

In order to enable those skilled in the art to understand the technical solutions of the present application more clearly, the technical solutions of the present application will be described in detail below with reference to specific embodiments.

This embodiment is described with a tensile test, the middle section of the test piece is used to measure the tensile deformation, and the length l ₀ of this section is called "gauge length". The thicker part at both ends is the head. In order to fit into the inner part of the chuck of the testing machine, the shape of the head of the specimen depends on the requirements of the chuck of the testing machine. Figure 4 shows the schematic diagram of the shape and size of the specimen. In this example, l ₀ =80mm. The specific test steps are as follows:

(1) Spray the black and white speckle pattern on the 3D printed sample. After drying, use the tensile fixture equipped with the universal testing machine to install the sample in the universal testing machine, and connect the universal testing control system to the universal testing machine. . Open the universal testing machine software to record the loading displacement, speed and force of the specimen in real time, and draw the tension-displacement curve in real time.

(2) Connect the CCD industrial camera to the computer, open the camera acquisition software VIC-2D, and debug the CCD industrial camera, so that the camera lens is focused on the specimen observation area. And set the camera sampling frequency to 2 frames per second.

(3) Turn on the universal testing machine, and use the typical DIC software VIC-2D software to start the CCD camera. While loading the specimen in tension through the fixture of the testing machine, the full-field deformation of the specimen is collected in real time with a CCD camera, with a sampling frequency of 2 frames per second, and is automatically saved to a designated folder with a numerical sequence number to obtain the loading process. Sequence images of the deformation of the test piece. Such as: Image001, Image002, Image003, …….

(4) Until the tensile failure of the specimen occurs, the test ends. The CCD camera stops capturing pictures. Save all acquired data.

(5) Use the DIC method to process the saved sequence images, compare and analyze all the sequence images and Image001, and calculate through the process shown in Figure 5 to obtain the displacement field and strain field in all subsequent states. Field analysis can be used to obtain parameters such as deformation speed, acceleration, and elongation of the specimen. Combined with the information of the loading displacement and force of the specimen collected by the universal testing machine, the elastic modulus and Poisson's ratio of the specimen are obtained.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. a method for analyzing the mechanical properties of 3D printing samples with different construction orientations, is characterized in that, comprises the following steps: 3D printing is used to make a variety of sample splines with different construction orientations, and speckle is set on the surface of the sample splines; Place the sample spline on the loading device and debug the loading device; Carry out the mechanical property testing test, and collect the image of the sample spline during the test; Using the digital image correlation method, the images before and after the deformation of the sample spline were compared and analyzed, and the pixel point displacement and strain information were obtained; According to the strain information, the stress-strain curve is obtained, and the performance parameters of the sample spline are obtained; The above steps are repeated to complete the mechanical property testing tests of the sample splines with different construction orientations, and the differences in the mechanical properties of the specimen splines with different construction orientations are analyzed. 2. The method for analyzing the mechanical properties of 3D printing samples with different construction orientations as claimed in claim 1, wherein the step of setting speckles on the surface of the sample splines is: The surface of one side of the sample spline is sprayed with white matte paint, and then decorated with black matt paint to make evenly distributed speckles. 3. The method for analyzing the mechanical properties of 3D printing samples with different construction orientations as claimed in claim 1, wherein the step of setting speckles on the surface of the sample splines is: The surface of one side of the sample spline is sprayed with black matte paint, and then decorated with white matt paint to make evenly distributed speckles. 4. The method for analyzing the mechanical properties of 3D printing samples with different construction orientations as claimed in claim 1, wherein the loading device comprises a universal testing machine, the universal testing machine is connected with the universal testing control system, and the universal testing machine is placed in front of the There is a CCD industrial camera, which is connected with a computer; the universal testing machine is provided with a clamping and loading member. 5 . The method for analyzing the mechanical properties of 3D printed samples with different construction orientations according to claim 4 , wherein when the three-point bending test is performed, the clamping loading member comprises a slideway, and the top of the slideway has a runner. 6 . In the chute, two loading supports are arranged on the chute at intervals, and the loading supports can slide along the chute; a concentrated force applying device is arranged above the chute. 6. The method for analyzing the mechanical properties of 3D printing samples with different construction orientations as claimed in claim 5, wherein the concentrated force applying device comprises a C-shaped member with an opening facing upward, and the top of the C-shaped member is connected to a universal testing machine , the bottom end of the C-shaped member is connected with a loading rod, and the loading rod is arranged vertically; the slideway is arranged horizontally. 7. The method for analyzing the mechanical properties of 3D printing samples with different construction orientations as claimed in claim 4, wherein the process of placing the sample splines is: Place the sample bar in the middle of the universal testing machine, so that the sample bar maintains a vertical and horizontal balance, and the speckle side of the sample bar faces the CCD industrial camera. 8. The method for analyzing the mechanical properties of 3D printing samples with different construction orientations as claimed in claim 1, wherein the acquisition process of pixel point displacement and strain information is: The images before and after deformation of the sample spline are compared and analyzed, and then the correlation calculation is performed on the sub-areas of the image before and after deformation, and the relative displacement of the pixel at the center point of the sub-area before and after deformation is obtained, so as to obtain the pixel point displacement and strain information. 9. The method for analyzing the mechanical properties of 3D printing samples with different construction orientations as claimed in claim 1, wherein the process of obtaining the performance parameters of the sample splines is: From the pixel point displacement and strain information, combined with the relationship between the loading load and time, the real-time stress-strain curve is obtained, and the strain cloud map obtained by the digital image correlation method is used to obtain the tensile strength, elongation, deformation speed and Acceleration performance parameters. 10. The method for analyzing the mechanical properties of 3D printing samples with different construction orientations according to claim 1, wherein the mechanical property testing test includes a tensile test, a compression test, and a three-point bending test. Oriented specimen splines were subjected to three tests in sequence to analyze the mechanical properties of specimen splines with different construction orientations under each test condition.

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